Fix: initialize currentHighlights @State from highlights parameter for first-render correctness

[R2kashyap]

Summary

Fixes a bug where AnimatedBodyContainer doesn't render highlights on first appearance. Users see an empty body view until they interact with it (tap a muscle, toggle front/back), which forces re-instantiation and a fresh render.

The Bug

AnimatedBodyContainer.currentHighlights is a @State property initialized to an empty dictionary:

@State private var currentHighlights: [Muscle: MuscleHighlight] = [:]

The rendering flow on first appearance:

1. SwiftUI creates AnimatedBodyContainer with highlights parameter containing heatmap data
2. @State currentHighlights initializes to [:] (empty)
3. body is evaluated — Canvas draws using blendedHighlights(progress: 1.0) which returns currentHighlights (empty)
4. View appears on screen showing no highlights
5. .onAppear fires, sets currentHighlights = highlights
6. Canvas does not automatically redraw from that @State change
7. User sees empty body until interaction forces re-render

The Fix

Initialize @State directly from the highlights parameter using the standard SwiftUI pattern for external initial values:

init(..., highlights: [Muscle: MuscleHighlight], ...) {
    // ... other assignments
    self._currentHighlights = State(initialValue: highlights)
}

Now the first Canvas draw has correct data. The .onAppear is no longer needed (removed). The .onChange(of: highlights) path is preserved for subsequent updates when highlights change after initial render.

How to Reproduce

// In a parent view that loads data asynchronously:
BodyView(gender: .male, side: .front)
    .heatmap([
        MuscleIntensity(muscle: .chest, intensity: 0.8),
        MuscleIntensity(muscle: .biceps, intensity: 0.5)
    ])
    .animated(duration: 0.3)

Before fix: Body renders without colors on first appearance. Toggle front/back to see colors.

After fix: Colors render immediately on first appearance.

Changes

• Sources/MuscleMap/Views/AnimatedBodyView.swift
  • Added explicit init that initializes _currentHighlights via State(initialValue: highlights)
  • Removed .onAppear { currentHighlights = highlights } (no longer needed)
  • Changed @State private var currentHighlights: [Muscle: MuscleHighlight] = [:] to remove default initializer

Testing

• Verified in production app with heatmap data present on first render
• Verified .onChange(of: highlights) still works for subsequent updates
• Verified front/back toggle still animates correctly